Voltage Sensitive Dyes act as optical transducers of membrane potential. Accordingly, they hold great promise in the study of two dimensional phenomena where a particular neural tissue is amenable to optical inspection. During the last year at the University of Pittsburgh, Dr. Salama and I demonstrated the feasibility of using one particular dye (NK2367) in the study of organizational features of macaque striate cortex. Subsequent to this we uncovered organizational features of macaque striate cortex that probably could not have been deduced with any other currently known technique. Funds are requested in this proposal for technical support and for supplies to continue these efforts. Specific experiments that are targeted for further efforts are outlined and include: 1) technical improvements, 2) further examination of ocular dominance column organization and attempts to find depth selective zones for both areas 17 and 18, 3) analysis of other representations of the visual field in striate cortex (for example, the foveal representation), and 4) correlation with anatomically demonstrated microcircuitry that can be revealed either with cytochrome oxidase or from transport following micro-injections of HRP. It is important to stress that, even though our current technique for using Voltage Sensitive Dyes can stand improvement, technical breakthroughs are not needed to achieve any of the scientific goals outlined in experiments 2-4. While it is not yet clear which of these experiments will prove most fruitful, they all can be investigated more or less simultaneously; and the successful completion of any one of them would constitute a significant advance in our understanding of visual cortical phenomena.